Shell-Structured Particles for Sunscreen Applications

ABSTRACT

Shell-structured particles for sunscreen applications are provided herein. A method includes selecting one or more particles to serve as a core material in a sunscreen composition, wherein each of the one or more particles comprises a band gap within a predetermined range, and wherein said selecting is based on a desired absorption spectrum of the sunscreen composition; coating the one or more particles with at least one layer of zinc oxide.

FIELD

The present application generally relates to chemical technology, and,more particularly, to sunscreen technologies.

BACKGROUND

Sunscreen creams and other such compositions are commonly used toprevent ultraviolet (UV) radiation (also referred to herein as “light”in this context) from reaching the skin of a human user and causingdamage. It is noted that UV light is an electromagnetic radiation with awavelength range between approximately 280 nanometers (nm) andapproximately 400 nanometers (specifically, that is the range of UVradiation that is not absorbed by the ozone).

A common active ingredient of existing sunscreen compositions is zincoxide (ZnO). ZnO is a semiconductor that has a specific band gap, andparticles of ZnO used in existing sunscreen compositions are typicallyapproximately 50-300 nm in size. Additionally, in existing sunscreencompositions, typical ZnO materials are capable of absorbing UV light(that is, blocking the UV light from passing through the sunscreencomposition to be absorbed by the skin of the user) within a wavelengthrange of approximately 290 nm through only approximately 350-380 nm.

Additionally, high sun protection factor (SPF) sunscreen compositions,which can absorb a large majority of the UV light in the range of290-380 nm, require the addition of a higher density of ZnO particles,which causes the composition to become white and/or opaque due to lightscattering from the ZnO particles, and which is an often undesirableproperty to consumers.

SUMMARY

In one embodiment of the present invention, oxide-based nanoparticlesfor use in sunscreen applications are provided. An exemplary method caninclude selecting one or more particles to serve as a core material in asunscreen composition, wherein each of the one or more particlescomprises a band gap within a predetermined range, and wherein saidselecting is based on a desired absorption spectrum of the sunscreencomposition; coating the one or more particles with at least one layerof zinc oxide.

In another embodiment of the invention, a sunscreen composition caninclude one or more particles constituting a core material in asunscreen composition, wherein each of the one or more particlescomprises a band gap within a predetermined range, and wherein said oneor more particles are selected based on a desired absorption spectrum ofthe sunscreen composition; and at least one layer of zinc oxideparticles coating the one or more selected particles.

Additionally, in one embodiment of the present invention, an exemplarymethod can include selecting one or more particles to serve as a coatinglayer in a sunscreen composition, wherein each of the one or moreparticles comprises a band gap within a predetermined range, and whereinsaid selecting is based on a desired absorption spectrum of thesunscreen composition; and coating one or more zinc oxide particles withthe one or more selected particles.

In yet another embodiment of the invention, a sunscreen composition caninclude one or more zinc oxide particles constituting a core material ina sunscreen composition; and one or more particles coating the one ormore zinc oxide particles, wherein each of the one or more particlescomprises a band gap within a predetermined range, and wherein said oneor more particles are selected based on a desired absorption spectrum ofthe sunscreen composition.

These and other objects, features and advantages of the presentinvention will become apparent from the following detailed descriptionof illustrative embodiments thereof, which is to be read in connectionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram illustrating a core-shell structure, according toan exemplary embodiment of the invention;

FIG. 1B is a diagram illustrating a core-shell structure with ananti-reflective coating (ARC), according to an exemplary embodiment ofthe invention;

FIG. 2A is a diagram illustrating a core-shell structure, according toan exemplary embodiment of the invention;

FIG. 2B is a diagram illustrating a core-shell structure with an ARC,according to an exemplary embodiment of the invention;

FIG. 3 is a flow diagram illustrating techniques according to anembodiment of the invention; and

FIG. 4 is a flow diagram illustrating techniques according to anembodiment of the invention.

DETAILED DESCRIPTION

As described herein, an embodiment of the present invention includesshell-structured particles for sunscreen applications. As furtherdetailed herein, one or more embodiments of the invention includegenerating compositions and methods of use thereof for effectivelyblocking more and/or all of the complete spectrum of UV light (that is,as noted above, the UV radiation that is not absorbed by the ozone, andwhich ranges between approximately 280 nm and 400 nm) while alsopreventing whitening effects caused by the scattering of light in thevisible spectrum (that is, radiation between approximately 400 nm and700 nm).

At least one embodiment of the invention includes introducing a copperoxide (Cu₂O) particle or coating layer to form a ZnO—Cu₂O or Cu₂O—ZnOcore-shell structure particle for use in sunscreen compositions. Asdetailed herein, utilization of Cu₂O (and/or analogous materials) canprovide extended optical absorption (for sunscreen compositions) ofwavelengths of light up to approximately 500 nm. The degree and/or therange of such extended absorption can be controlled by the size of theCu₂O particle, the thickness of the Cu₂O coating, and/or the volumeratio between ZnO and Cu₂O.

As noted, in at least one embodiment of the invention, the Cu₂O materialcan be replaced with one or more other materials having a band gap ofapproximately 2-3 electron volts (eV), such as, for example, zincoxy-sulfide (ZnOS), ZnO_(x)S_(1-x), wherein 0≦x≦1, indium sulfide(In₂S₃), indium oxy-sulfide (In₂(O_(x)S_(y1-x))₃, wherein 0≦x≦1, orcombinations thereof. Such materials can be utilized, alone or incombination, to tune the absorption spectrum of the sunscreencomposition.

In one or more embodiments of the invention, the core portion of acore-shell structure can include a single particle or multipleparticles. Additionally, in at least one embodiment of the invention,the surface of the core-shell structure can be roughened to providereduced optical reflection.

Further, as detailed herein, one or more embodiments of the inventioncan include applying an ARC to the outside and/or exterior surface ofthe core-shell particles to minimize reflection from the particles. Insuch an embodiment, the ARC can include any material having a refractiveindex between that of ZnO (or Cu₂O) and air (or surrounding media),which allows light to better couple into the core-shell particlestructure and limits and/or prevents scattering at the ZnO (Cu₂O)interface. Such materials can include, for example, silicon dioxide(SiO₂), magnesium fluoride (MgF₂), fluoropolymers, etc.

Additionally, in such an embodiment, the ARC can include a single layeror can be comprised of multiple layers, wherein the refractive index ofthe layers are graded between that of the ZnO (or Cu₂O) and that of thesurrounding media (such as air). Further, an ARC utilized in one or moreembodiments of the invention can be dense or porous, wherein porouslayers can contain an effective refractive index between that of air andthat of the coating and/or shell material. Additionally, an ARC utilizedin one or more embodiments of the invention can be smooth or roughened,wherein roughened layers can contain an effective refractive indexbetween that of air and that of the coating and/or shell material.

FIG. 1A is a diagram illustrating a core-shell structure, according toan exemplary embodiment of the invention. Specifically, FIG. 1A depictsa Cu₂O core 102 coated by a ZnO shell 104. Additionally, FIG. 1B is adiagram illustrating a core-shell structure with an ARC, according to anexemplary embodiment of the invention. Specifically, FIG. 1B depicts aCu₂O core 102 coated by a ZnO shell 104, and the core-shell structurefurther coated by an ARC layer 106 (such as, for example, SiO₂).

FIG. 2A is a diagram illustrating a core-shell structure, according toan exemplary embodiment of the invention. Specifically, FIG. 2A depictsa ZnO core 104 coated by a Cu₂O shell 102. Additionally, FIG. 2B is adiagram illustrating a core-shell structure with an ARC, according to anexemplary embodiment of the invention. Specifically, FIG. 2B depicts aZnO core 104 coated by a Cu₂O shell 102, and the core-shell structurefurther coated by an ARC layer 106 (such as, for example, SiO₂).

FIG. 3 is a flow diagram illustrating techniques, according to anembodiment of the present invention. Step 302 includes selecting one ormore particles to serve as a core material in a sunscreen composition,wherein each of the one or more particles comprises a band gap within apredetermined range (for example, between approximately two and threeeV), and wherein said selecting is based on a desired absorptionspectrum of the sunscreen composition. The one or more particles caninclude one or more copper oxide particles. Step 304 includes coatingthe one or more particles with at least one layer of zinc oxide.

The techniques depicted in FIG. 3 can also include adjusting the desiredabsorption spectrum of the sunscreen composition by adjusting the sizeof the one or more selected particles, adjusting the thickness of the atleast one layer of zinc oxide coating the one or more particles, and/oradjusting the volume ratio between the one or more particles and the atleast one layer of zinc oxide.

Additionally, the techniques depicted in FIG. 3 can include manipulatingthe surface of the at least one layer of zinc oxide coating the one ormore particles to form a roughened surface. Further, at least oneembodiment of the invention can include applying an anti-reflectivecoating to the surface of the at least one layer of zinc oxide, whereinthe anti-reflective coating comprises a material having a refractiveindex within a predetermined range.

Also, an additional embodiment of the invention includes a compositionthat includes one or more particles constituting a core material in asunscreen composition, wherein each of the one or more particlescomprises a band gap within a predetermined range, and wherein said oneor more particles are selected based on a desired absorption spectrum ofthe sunscreen composition; and at least one layer of zinc oxideparticles coating the one or more selected particles. Such a compositioncan also optionally include an anti-reflective coating applied to thesurface of the at least one layer of zinc oxide, wherein theanti-reflective coating comprises a material having a refractive indexwithin a predetermined range.

FIG. 4 is a flow diagram illustrating techniques, according to anembodiment of the present invention. Step 402 includes selecting one ormore particles to serve as a coating layer in a sunscreen composition,wherein each of the one or more particles comprises a band gap within apredetermined range (for example, between approximately two and threeeV), and wherein said selecting is based on a desired absorptionspectrum of the sunscreen composition. The one or more selectedparticles can include one or more copper oxide particles. Step 404includes coating one or more zinc oxide particles with the one or moreselected particles.

The techniques depicted in FIG. 4 can also include adjusting the desiredabsorption spectrum of the sunscreen composition by adjusting the sizeof the one or more selected particles, adjusting the thickness of theone or more particles coating the one or more zinc oxide particles,and/or adjusting the volume ratio between the one or more selectedparticles and the one or more zinc oxide particles.

Additionally, the techniques depicted in FIG. 4 can include manipulatingthe surface of the one or more particles coating the one or more zincoxide particles to form a roughened surface. Further, at least oneembodiment of the invention can include applying an anti-reflectivecoating to the surface of the one or more particles coating the one ormore zinc oxide particles, wherein the anti-reflective coating comprisesa material having a refractive index within a predetermined range.

Further, yet another embodiment of the invention includes a compositionthat includes one or more zinc oxide particles constituting a corematerial in a sunscreen composition; and one or more particles coatingthe one or more zinc oxide particles, wherein each of the one or moreparticles comprises a band gap within a predetermined range, and whereinsaid one or more particles are selected based on a desired absorptionspectrum of the sunscreen composition. Such a composition can alsoinclude an anti-reflective coating applied to the surface of the one ormore particles coating the one or more zinc oxide particles, wherein theanti-reflective coating comprises a material having a refractive indexwithin a predetermined range.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, steps, operations, elements, and/orcomponents, but do not preclude the presence or addition of anotherfeature, step, operation, element, component, and/or group thereof.

At least one embodiment of the present invention may provide abeneficial effect such as, for example, generating extended opticalabsorption of wavelengths of light up to approximately 500 nm.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A method, comprising: selecting one or moreparticles to serve as a coating layer in a sunscreen composition,wherein each of the one or more particles comprises a band gap within apredetermined range, and wherein said selecting is based on a desiredabsorption spectrum of the sunscreen composition; and coating one ormore zinc oxide particles with the one or more selected particles. 2.The method of claim 1, wherein the one or more selected particlescomprise one or more copper oxide particles.
 3. The method of claim 1,wherein the one or more selected particles comprise one or more zincoxy-sulfide particles.
 4. The method of claim 1, wherein the one or moreselected particles comprise one or more indium sulfide particles.
 5. Themethod of claim 1, wherein the one or more selected particles compriseone or more indium oxy-sulfide particles.
 6. The method of claim 1,wherein the predetermined band gap range comprises between approximatelytwo and three electron volts.
 7. The method of claim 1, furthercomprising: adjusting the desired absorption spectrum of the sunscreencomposition by adjusting the size of the one or more selected particles.8. The method of claim 1, further comprising: adjusting the desiredabsorption spectrum of the sunscreen composition by adjusting thethickness of the one or more particles coating the one or more zincoxide particles.
 9. The method of claim 1, further comprising: adjustingthe desired absorption spectrum of the sunscreen composition byadjusting the volume ratio between the one or more selected particlesand the one or more zinc oxide particles.
 10. The method of claim 1,further comprising: manipulating the surface of the one or moreparticles coating the one or more zinc oxide particles to form aroughened surface.
 11. The method of claim 1, further comprising:applying an anti-reflective coating to the surface of the one or moreparticles coating the one or more zinc oxide particles, wherein theanti-reflective coating comprises a material having a refractive indexwithin a predetermined range.
 12. The method of claim 11, wherein thematerial comprises silicon dioxide.
 13. The method of claim 11, whereinthe material comprises magnesium fluoride.
 14. The method of claim 11,wherein the material comprises one or more fluoropolymers.